Aromatic polycarbonate resins have been used as general-purpose engineering plastics in various extensive applications such as parts of electric, electronic and OA equipments, mechanical parts and vehicle parts because the resins are excellent in various properties such as transparency, impact resistance, heat resistance and dimensional stability. In addition, polymer alloys comprising an aromatic polycarbonate resin and a thermoplastic polyester resin are known as materials that are improved in chemical resistance and moldability as poor properties of the aromatic polycarbonate resins while maintaining the above excellent properties inherent to the aromatic polycarbonate resins, and have been used in the applications such as interior and exterior parts and outside plate parts for vehicles and various housing members, as well as in the other extensive applications.
In order to improve a rigidity and a dimensional stability of the polymer alloys comprising an aromatic polycarbonate resin and a thermoplastic resin other than the aromatic polycarbonate resin such as a thermoplastic polyester resin, in general, there is widely known a method of incorporating an inorganic filler such as glass fiber and talc into the polymer alloys. However, when the glass fiber is blended in the polymer alloys, a molded product obtained from such polymer alloys tends to be deteriorated in appearance on the surface thereof, resulting in only limited applications to exterior parts and outside plate parts for vehicles requiring a good appearance.
On the other hand, although the resin composition containing a talc provides a molded product having a good appearance, decomposition of the aromatic polycarbonate resin as well as transesterification reaction between the aromatic polycarbonate resin and the thermoplastic polyester resin tend to excessively proceed owing to a strong basicity of the talc, resulting in poor thermal stability of the resin composition.
In particular, there is such a recent tendency that exterior parts and outside plate parts for vehicles are required to have a large size and a high rigidity as a molded product. Therefore, it has been demanded to provide such a material capable of exhibiting excellent thermal stability and impact resistance. Also, as to the impact resistance required for these molded products, an elongation at break or a surface impact strength becomes more important than Izod impact strength owing to the relation with strain rate. As a result, it is required to provide a material capable of improving these impact properties by blending a talc in the resin composition.
To solve the problem concerning poor thermal stability of the resin composition when blending a talc therein, there have been proposed a resin composition containing a specific rubber polymer (for example, refer to Patent Document 1), a resin composition containing a specific phosphorus-based stabilizer (for example, refer to Patent Documents 2 and 3), and a resin composition using a surface-treated talc (for example, refer to Patent Document 4). However, in these conventional techniques, the obtained resin compositions tend to be unsatisfactory in thermal stability and impact resistance. Therefore, it has been strongly required to improve these properties of the resin compositions.
On the other hand, there have been proposed a resin composition using a talc that is increased in bulk specific gravity by mechanical compression (for example, refer to Patent Documents 5 and 6), and a resin composition using a talc having a limited electric conductivity (for example, refer to Patent Document 7). In the Patent Document 7, it is described that the talc is preferably in the form of a compressed and granulated product, and the talc may be granulated using a binder.
However, in the conventional techniques specifically illustrated in these Patent Documents, the obtained resin compositions are still unsatisfactory in thermal stability and impact resistance. Further, in Patent Document 8, there has been proposed the technique concerning such a talc that is formed into granules using a binder, and it is described that polycarbonate resins, polyester resins, rubber-based resins as well as plural kinds of these resins may be used as the binder. However, the technique described in the Patent Document 8 neither teaches nor suggests the above problems caused upon blending the talc in the aromatic polycarbonate resins. Therefore, it is not possible to obtain a resin composition having satisfactory thermal stability and impact resistance only by blending the granular talc in the aromatic polycarbonate resins.
In addition, although the aromatic polycarbonate resins have been used in extensive applications, among them, in the applications such as parts of electric, electronic and OA equipments, these products have been strongly required to exhibit especially a good flame retardancy. For this reason, there is extensively known such a general technique of blending various flame retardants in the aromatic polycarbonate resins to impart a good flame retardancy thereto.
As the resin composition containing a flame retardant, such resin compositions containing a halogen-based flame retardant such as bromine compounds have been used for a long time. These resin compositions exhibit a high flame retardancy, but suffer from the problem concerning high burden on environments. Therefore, there have been proposed a number of resin compositions containing a non-halogen-based flame retardant.
Further, the aromatic polycarbonate resins tend to be deteriorated in fluidity. Therefore, resin compositions obtained by incorporating an organic phosphate-based flame retardant into a polymer alloy comprising an aromatic polycarbonate resin and a styrene-based resin such as acrylonitrile-butadiene-styrene copolymer (ABS resin) have been extensively used especially in the applications of housings for OA equipments such as personal computers and printers.
In recent years, in the applications of parts of electric, electronic and OA equipments, the thickness thereof has been rapidly reduced, so that it has been demanded to provide a material capable of exhibiting a good appearance and a high rigidity. For instance, there has been proposed a flame-retardant resin composition containing an inorganic filler having a small particle size such as talc (for example, refer to Patent Document 9). However, the resin compositions obtained by blending the talc in aromatic polycarbonate resins tend to suffer from problems such as decomposition of the aromatic polycarbonate resins and, therefore, poor thermal stability and impact resistance owing to a strong basicity of the talc, notwithstanding such an advantage that the molded product obtained therefrom can exhibit a good appearance. Further, the resin compositions containing the non-halogen-based flame retardant also tend to suffer from such a problem that the flame retardancy of these compositions is deteriorated as the content of the talc therein increases.
To solve the above problems, there has been proposed a flame-retardant resin composition containing a surface-treated inorganic filer (for example, refer to Patent Documents 10 to 12). However, in the conventional techniques described in these Patent Documents, the obtained resin compositions are still unsatisfactory in flame retardancy and thermal stability. Further, when blending a talc having a small particle size in the resin compositions, there tend to arise problems such as clogging of a hopper, deteriorated extrusion moldability such as poor intrusion into an extruder, and poor impact resistance of the resultant resin composition owing to poor dispersion of the talc therein.
As described above, in the application fields of the thermoplastic resin compositions comprising an aromatic polycarbonate resin into which a talc having a small particle size and a non-halogen-based flame retardant are blended, it has been strongly demanded to develop the techniques for enhancing an extrusion moldability, a rigidity, a flame retardancy, an impact resistance and a thermal stability thereof.
To solve the above conventional problems, there have been proposed a resin composition using a talc that is increased in bulk specific gravity by mechanical compression (for example, refer to Patent Document 5), and a resin composition using a talc having a limited electric conductivity (for example, refer to Patent Document 7). In particular, in the Patent Document 7, it is described that the talc is preferably in the form of a compressed and granulated product, and the talc may be granulated using a binder. However, in these Patent documents, no specific examples concerning such features of the resin compositions are described, and further the obtained resin compositions are still unsatisfactory in extrusion moldability, flame retardancy, impact resistance and thermal stability.
On the other hand, there have been proposed the technique concerning an inorganic filler that is formed into a granular shape using a binder (for example, refer to Patent Document 8), and a thermoplastic resin composition obtained by blending a granular talc granulated using a specific amount of bentonite, in an aromatic polycarbonate resin (for example, refer to Patent Document 13). However, in these Patent Documents, it is merely described that the flame retardant may be blended in the composition, but there is no description concerning a resin composition comprising an aromatic polycarbonate resin, and a granular talc and a non-halogen-based flame retardant blended in the resin which is excellent in flame retardancy and thermal stability.
Patent Document 1: Japanese Patent Application Laid-Open (KOKAI) No. 2001-294741
Patent Document 2: Japanese Patent Application Laid-Open (KOKAI) No. 5-222283 (1993)
Patent Document 3: Japanese Patent Application Laid-Open (KOKAI) No. 6-49343 (1994)
Patent Document 4: Japanese Patent Application Laid-Open (KOKAI) No. 8-127711 (1996)
Patent Document 5: Japanese Patent Application Laid-Open (KOKAI) No. 8-176339 (1996)
Patent Document 6: Japanese Patent Application Laid-Open (KOKAI) No. 10-101914 (1998)
Patent Document 7: Japanese Patent Application Laid-Open (KOKAI) No. 2002-60637
Patent Document 8: Japanese Patent Application Laid-Open (KOKAI) No. 2002-220549
Patent Document 9: Japanese Patent Application Laid-Open (KOKAI) No. 2003-134304
Patent Document 10: Japanese Patent Application Laid-Open (KOKAI) No. 10-338805 (1998)
Patent Document 11: Japanese Patent Application Laid-Open (KOKAI) No. 2005-48072
Patent Document 12: Japanese Patent Application Laid-Open (KOKAI) No. 2005-220216
Patent Document 13: Japanese Patent Application Laid-Open (KOKAI) No. 2006-77176